1. Field of Invention
This inventions relates to an improved laminated article with an improved integral flexible hinge and methods for manufacturing laminated articles.
2. Description of Prior Art
There are a variety of flexible hinges known in the prior art. For example, in U.S. Pat. No. 4,636,065 a flexible hinge is disclosed that attempts to solve the stress and durability problems associated with the folding of a copier cover plate. The design solution involves setting back one end of the edges of the cover plate at an angle to avoid shearing forces. Another example of a flexible hinge is disclosed in U.S. Pat. No. 3,615,035 for the lid of a pharmaceutical box. The unique assembly problems associated with a box lid are solved by a tongue and groove design. Another example of a flexible hinge is disclosed in U.S. Pat. No. 3,167,207 for a plastic container. The need for a firm container body yet a flexible hinge is solved by having integral hinge anchor lugs on the container adapted to engage a separate flexible hinge assembly.
While is clear that the design in each of the above cases represents an attempt to solve the unique problems associated with the folding of the leaves of the particular article requiring a hinge, there is also a problem common to all of the cases. This problem is the incompatibility of a flexible hinge with sturdy leaves. That is to say, if the article is to be cast as a single piece from sturdy material, the hinge will have the sturdy characteristics of the leaves and will not be flexible. On the other hand, if the article is to be cast as a single piece from flexible material, the hinge will be flexible while the leaves will not be sturdy. This problem is significant when considering large scale manufacture where a monolithic design could result in significant cost savings.
The present invention involves the joining of two or more laminated leaves of an article together. The problem of joining laminated leaves together inexpensively such that they might fold against each other easily and tightly has been approached in the past in two predominant ways.
The most common solution is that employed in restaurant menu construction. The leaves in this case are pages, printed side by side on a single sheet of paper. This sheet of paper is then laminated by conventional means with relatively thin laminating film (usually a polypropylene/mylar film of approximately 0.008 centimeters or less), and subsequently folded in half to create a crude hinge apparatus. Sometimes the paper is scored during the printing process prior to lamination to facilitate folding.
The advantage of this process is that it is easy to accomplish. There are many disadvantages, however, to this method. First and foremost, because the web of the hinge apparatus is the exact same material and thickness as the leaves, the hinge apparatus of this type exhibits a significant bending resistance. Because of bending resistance, hinges of this type of construction have the disadvantage that the leaves are very limited in their degree of pivot and ease of pivot. Furthermore, because of the extent of bending resistance relative to the weight of the leaves, the web of the hinge apparatus exhibits memory. Memory is defined as the tendency of the web via bending resistance to cause the leaves to retreat to a prior position after manipulation to a new position. Memory is most commonly observed when a menu is opened flat on a table top; the menu resists the 180.degree. angle and the pages retreat toward the closed position.
There are other disadvantages that stem from the bending resistance of the web. For example, because the hinge means cannot effectively open up to 360.degree., the order of the pages cannot be reversed, precluding the ability to study any side of either page with the article in its most compact configuration. Similarly, because of bending resistance there is difficulty in handling, low durability, and a sense of overall inferior quality for the user. All of these problems are, of course, compounded with multi-page articles.
A rarely utilized solution to the overall problem involves the use of book tape, an adhesive backed, 1"-2" wide, polypropylene tape. The two pages are printed on separate sheets of paper and then individually laminated. The two sheets are aligned by hand, edge to edge with a small gap, and then taped by hand with the book tape (preferably on both the front and back sides of the joint).
The advantage of this method is that it overcomes some of the disadvantages mentioned above. There are, however, disadvantages with this method as well. First, because of the hand labor involved in assembly, the article is not easily produced (especially in quantity) and is therefore expensive to make. Second, because the tape is not invisible, there is a distinct line at its edges that partially clouds the image underneath it. Third, the tape's adhesive is not as permanent as the laminated pages. Fourth, the tape's adhesive is subject to oozing at warm temperatures. Finally, the tape's adhesive collects dirt at the edge of the tape.
The present invention avoids these disadvantages. The present invention provides a laminated article of two or more leaves with an improved hinge and methods for manufacturing the same. When the leaves are to display printed matter, the present invention provides hingedly joined leaves in a suitable format for such articles as maps, menus, references, and guides.
This improved hinge pivots easily. Moreover, the bending resistance of the web does not act to change the position of the leaves it connects. The hinge opens from 0 to 360.degree. and yet allows rigid, substantial leaves. The hinge is integral and invisible in its attachment, and yet is as durable as the leaves it connects. The invention thereby solves the incompatibility problem associated with monolithic designs. Furthermore, the improved hinge neither gathers dirt nor obscures any image that might be printed on the leaves in any way. Importantly, this improved hinge is simple, inexpensive, and readily assembled in quantity.
Readers will find further objects and advantages of the invention from a consideration of the ensuing description and the accompanying drawings.